1. Field of Invention
The present invention relates to a battery in a mobile terminal (e.g., laptop computer, smart mobile phone) having a rechargeable battery, and more particularly, to a method and an apparatus of charge management for a battery in a mobile terminal.
2. Description of Prior Art
Power modes for a mobile terminal, such as laptop computer, are generally classified into two types, a battery-powered mode and an alternating-current (AC)-powered mode. The mobile terminal is powered by a rechargeable battery in the battery-powered mode, while it is powered by an AC source, to be specific, an external direct-current (DC) source provided by an AC/DC adapter, in the AC-powered mode. At this point, the rechargeable battery may be in a standby state or a charge state. Explanation will be given by example of a laptop computer.
Problems often occur during use of a battery in a laptop computer. More specifically, for a laptop computer used at home or office, the AC-powered mode is often adopted, whereas the battery-powered mode is scarcely used. The natural discharge or sporadic use (e.g., the computer is turned on before it is connected to the AC source) of the battery will result in continuous and cyclic charge of the battery and consequently an accelerated aging process of the battery. In most situations, users find that the battery's lifetime is short although it is rarely used. The lifetime usually lasts for only one or two years. In an extreme situation, aging of the battery may pose higher risk of explosion of the battery.
FIG. 1 shows a charge process of a lithium battery in a laptop computer, in which it is in a trickle charge mode when the battery capacity is between 96% and 100%. Currently, a common charge strategy for a laptop computer battery is to set a charge start point (e.g., to start the charge process when the remaining capacity of the battery is <96%, as shown in FIG. 2) and a charge stop point (e.g., 100%, that is, to stop the charge process when the remaining capacity of the battery reaches 100%) so that the charge process is executed cyclically from the capacity of 96% to 100%. This can ensure that the battery is always in a full charge status so as to meet the users' requirement of using the laptop computer in a mobile manner at any moment. However, for those who rarely adopt the battery-powered mode, such charge strategy will inevitably cause a repeated charge operation of the battery and accelerate its aging process. As a result, the users who often use laptop computers at home have to replace the batteries every one or two years, while they had had little use of the batteries.
So far, some technical solutions have been proposed to manage the charging of a battery. For example, a switch that can be manipulated manually (pressed or pushed) by a user is designed so that a SMC signal between a battery pack and an embedded controller (EC) on a motherboard of a laptop computer is shorted to ground. As such, to the EC, it seems that no battery pack is present (a better way is to cut off a battery presence signal BAT_PRES#). As a result, the stop of any charging process depends on users' decisions. Nevertheless it is infeasible to require ordinary and unprofessional computer users to decide when the charging should be stopped.
Moreover, in a patent application No. 200510136210.4 filed with SIPO of China on Dec. 20, 2005, for example, a mechanism is provided for charging a battery in a mobile electronic device. This mechanism determines a suitable time for charging process based on the habitual charging time or location (i.e., the location of the mobile device) of the user of the electronic mobile device. Then, it determines whether the charging process needs to be started according to the remaining capacity. It also raises an issue of when it is necessary to charge the battery in order to notify the user of such necessity. As can be seen, the mechanism is based on the user's habit, while most users cannot carry out the charging process in a correct way or a way in favor of battery lifetime. In fact, the habit of a user in charging a battery may not necessarily facilitate the maintenance of the battery or extension of the battery's lifetime. On the other hand, the implementation of such mechanism requires intervention from a user, which hinders a comfortable user experience.
It is desirable that a mobile terminal can automatically determine whether to charge its battery in favor of battery maintenance and enable different operations for different users, based on each user's usage and without any intervention from users.